Jazz bass pole piece length?

[tonemonkey]

I see alnico rod magnets sold all over the place but I don't know what the standard size for Jazz basses is. How long should they be and what should the diameter be?

I got it - .187 or .195 and .781 length. Would .375 x 1.0 work? I'm interested in making pickups with .375 diameter alnico 5 rods, but the only magnets I can find are .375 x 1.0 (like on a Stingray).

[big_teee]

I see alnico rod magnets sold all over the place but I don't know what the standard size for Jazz basses is. How long should they be and what should the diameter be?

I got it - .187 or .195 and .781 length. Would .375 x 1.0 work? I'm interested in making pickups with .375 diameter alnico 5 rods, but the only magnets I can find are .375 x 1.0 (like on a Stingray).

Welcome to the forum:
The larger the diameter of the magnet, The more of the winding area you lose.
The Jazz pickup flange is only .63 inches wide.
Now subtract .375, and there isn't much left.
I would stick with the .187 or .195 x .781.
with 2 magnets per string, you still have a lot of magnet area.
Good Luck,
Terry

[David Schwab]

...but the only magnets I can find are .375 x 1.0 (like on a Stingray).

Where did you find the Stingray magnets?

You can get .25" diameter magnets at Mojo now.

[David Schwab]

Welcome to the forum:
The larger the diameter of the magnet, The more of the winding area you lose.
The Jazz pickup flange is only .63 inches wide.
Now subtract .375, and there isn't much left.
I would stick with the .187 or .195 x .781.
with 2 magnets per string, you still have a lot of magnet area.
Good Luck,
Terry

Yeah, Stingrays have wide coils and don't have a lot of wire wound on them. But Jazz bobbins are pretty tall. You can even make them a little taller if you need to.

The closed Jazz covers at Mojo are extra tall, and then all you would need to do is drill some holes.

There are Jazz pickups made this way.



These are clearly steel poles with a ceramic magnet on the bottom. I also wouldn't be surprised if the poles were shaped like a flat head screw, and had a thinner section going through the coil.

[tonemonkey]

Where did you find the Stingray magnets?

You can get .25" diameter magnets at Mojo now.

They do have .25" magnets at Mojo but they're only .6" long - too short for Jazz Bass, right??

I found these .375" alnico magnets on ebay.

[David Schwab]

They do have .25" magnets at Mojo but they're only .6" long - too short for Jazz Bass, right??

Oh yeah, I didn't see what lengths they had.

The the .375 magnets, you could also make them longer by sticking a short length of the same diameter steel rod on the bottom.

[tonemonkey]

They do have .25" magnets at Mojo but they're only .6" long - too short for Jazz Bass, right??

Oh yeah, I didn't see what lengths they had.

The the .375 magnets, you could also make them longer by sticking a short length of the same diameter steel rod on the bottom.

In my searching I've found .375 magnets that are .6" and some that are 1" - either too long or too short. In truth, they're probably too wide to effectively use in Jazz pups, but Delano worked it out!

[big_teee]

Shea at Magnetic hold has a lot of diff. Length .25 Mags.
T
Pickup Mags2.xls

[David Schwab]

In my searching I've found .375 magnets that are .6" and some that are 1" - either too long or too short. In truth, they're probably too wide to effectively use in Jazz pups, but Delano worked it out!

They might not be wound like a regular Jazz pickup, or they might be using thinner wire. They also don't say those are alnico magnets. They might be steel poles, and might not go the entire height of he pole.

The P bass version has this description:

The big ferrous poles grab all the strings movements with zero loss. Specially engineered ferrite magnets and custom wound coils make up for a bass transducer ready to redefine the word PRECISION.

So they are steel poles and ceramic magnets.

[tonemonkey]

They might not be wound like a regular Jazz pickup, or they might be using thinner wire. They also don't say those are alnico magnets. They might be steel poles, and might not go the entire height of he pole.

The P bass version has this description:



So they are steel poles and ceramic magnets.

Gotcha! Thanks!

[FunkyKikuchiyo]

I don't know the exact math, but I do know that once you exceed certain dimensions it'll struggle to hold onto magnetism without some sort of keeper underneath. I don't know if that would be an issue for you, but something perhaps to lodge in the back of your head...

[tonemonkey]

It turns out that those are steel rods which sit on top of a ceramic magnet. It's not what I thought.

[David King]

It's funny, I never bothered to measure an actual J coil but I always assumed the magnets were .1875 x .750" -is that totally wrong??

[David Schwab]

It's funny, I never bothered to measure an actual J coil but I always assumed the magnets were .1875 x .750" -is that totally wrong??

No, that's right.

He was asking about over sized magnets for a Jazz pickup.

[David Schwab]

It turns out that those are steel rods which sit on top of a ceramic magnet. It's not what I thought.

Well that's not a bad thing though. Big alnicos can cause a lot of string pull.

The main thing is not just decided you want X size magnets. You have to come up with a pickup that sounds good with those magnets.

[tonemonkey]

Well that's not a bad thing though. Big alnicos can cause a lot of string pull.

The main thing is not just decided you want X size magnets. You have to come up with a pickup that sounds good with those magnets.

Does reducing the amount of wire in the coil reduce the pull?

[big_teee]

Does reducing the amount of wire in the coil reduce the pull?

No, it's the strength and size of the Magnets, that effect the string Pull!
David was probably suggesting that if you put steel poles between the strong magnet and and the strings.
It would reduce the string pull.
T

[tonemonkey]

No, it's the strength and size of the Magnets, that effect the string Pull!
David was probably suggesting that if you put steel poles between the strong magnet and and the strings.
It would reduce the string pull.
T

How do they do it on a Stingray pickup? They use .375 x .625 alnico 5 magnets.

[David King]

They didn't worry about string pull and I wouldn't either if I were going to build a MM style pickup.

[David Schwab]

I haven't spent too much time with MM basses, but I do know if you get Jazz or P pickups too close you will get that dreaded string warble.

All but one of the MM pickups I have installed for people had steel poles and ceramic magnet Duncans.